A conventional encoder has a rotating shaft inserted through an axial hole of an axis sleeve so that the rotating shaft rotates in the axial hole of the axis sleeve. The conventional encoder also has a stopping base on which an axial hole is defined to match with the axial hole of the rotating shaft, such that the stopping base rotates with the stopping base. Likewise, a stopping structure is fixed on the rotating shaft and the stopping base so as to limit a rotating angle of the rotating shaft, for example, the rotating shaft only rotates within 320 degrees. The stopping structure includes the rotating shaft and two stop blocks of the stopping base, so when the two stop blocks hit each other, the rotating shaft does not rotate forward but rotates backward. If the rotating angle (i.e., 320 degrees) of the rotating shaft is divided into 16 units, then each rotating unit is 20 degrees and corresponds to a channel, so there are 16 channels defined in the encoder. However, such a conventional stopping structure is encoded inconveniently. For example, a number of the channels is limited without being increased, thus limiting an encoding program.
Furthermore, the electrical brush is riveted with the movable arm, so the following defects occur. For instance, the electrical brush is riveted with the circuit plate insecurely, thus affecting the stability of the signal. Due to the electrical brush is riveted with the circuit plate at a high temperature, thermal expansion and contraction will loosen the electrical brush, thereby lowering a service life of the encoder. Moreover, the electrical brush is riveted with the circuit plate at the high temperature, a height between the brush head of the electrical brush and a bottom surface of the movable arm decreases 50%, so the electrical brush contacts with the circuit plate unstably.
Also, an elastic arm of the electrical brush is too short (i.e., a distance between a riveting point or a fulcrum and the brush head of the electrical brush is too short), so as the height of the brush head changes, the length of the electrical brush is too short, then an angle between the elastic arm and the arm seat changes greatly to loosen the electric brush, hence the electrical brush contacts the circuit plate unstably.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.